The invention relates to a device for writing information blocks in a track pattern on a record carrier of a rewritable type, which device is provided with a writing unit for writing areas of the record carrier via (i.e. by using) a beam of electromagnetic radiation with marks representing the information blocks, and positioning means for positioning the writing unit based on a track structure which defines a track pattern on the record carrier.
The invention also relates to a method of writing information blocks in a track pattern on a record carrier of the rewritable type. Marks representing the information blocks are written in areas of the record carrier via a writing unit via a beam of electromagnetic radiation. The writing unit is positioned on the basis of a track structure which defines the track pattern.
The invention further relates to a record carrier for use in the writing device.
Moreover, the invention relates to a reading device for reading information blocks represented by optically readable marks in a track pattern on a record carrier. The device is provided with a reading unit for reading the marks via a beam of electromagnetic radiation, and apparatus for positioning the reading unit on the basis of the marks.
A writing device, a method and a record carrier of the type described in the opening paragraph for writing information blocks are known from U.S. Pat. No. 4,901,300 (PHN 12.398). In the system described in that document, information blocks are recorded in a track pattern on the record carrier and represented by optically readable marks. The record carrier has a track structure in the form of a wobbling pregroove having a varying frequency which represents position information. The writing device has a write head for scanning the record carrier via a beam of electromagnetic radiation. The tracking signals are derived from reflected radiation. The writing device includes for positioning the write head during scanning based on the position information. During scanning, the wobble causes a modulation in the tracking signals. This modulation comprises the position information coded therein, which indicates the absolute position in the track with respect to the starting point of the area intended for information. The information blocks are recorded on the record carrier at a desired position in conformity with their address, while the write head is positioned, if necessary via a jump to another radial position in the track, on the basis of the position information. A record carrier may have been partly written and then includes written areas in which marks are present, and non-written areas in which only the track structure is present. There are reading devices which derive the tracking signals and/or position information from the marks.
The inventors recognize the position information can not be generated in non-written areas, so that a partly written record carrier is not reliably readable.
It is, inter alia, an object of the invention to provide apparatus with which a partly written record carrier can be read more reliably.
In accordance with a first aspect of the invention, a writing device is therefore characterized in that the device is provided with first detection means for detecting areas of the record carrier which are in use for writing information blocks, and second detection apparatus for detecting non-written boundary areas adjoining the areas which are in use, and initialization apparatus for writing the non-written boundary areas with dummy information. The writing device according to the invention has, inter alia, the advantage that partly written record carriers can be read reliably by reading devices which derive tracking signals and position information from marks, because boundary areas adjoining isolated information blocks have been written. When a radial jump to such an area is made, the reading unit will be globally positioned a short distance ahead of the information block to be read, for example, on the basis of distance information derived from a speed sensor on a motor for displacing the reading unit. The reading unit will then reach the adjoining area a short distance ahead of the information block to be read. In this area, the marks of the dummy information are present and the reading unit can therefore be accurately positioned in a conventional manner on the basis of information read from the record carrier. A further advantage is that boundary areas are written beyond the information block to be read, for the case where, due to inaccuracies during global positioning, the reading unit is positioned a short distance behind the information block to be read.
It is to be noted that a disc storage system is known from EP 0 328 240, in which the area on a disc-shaped record carrier intended for data storage is successively formatted in parts whenever a part is necessary for actual data storage. During formatting, areas are provided with position information before they are put into use and analyzed by way of writing and subsequent reading, with error control information being generated on the basis of the analysis. In the system according to the invention, the position information is already present in the track structure and areas which are not in use, namely the non-written boundary areas of areas which are in use, are written with dummy data by way of a writing action before or after an area for data storage has been put into use.
An embodiment of the device according to the invention is characterized in that the first detection apparatus are adapted i.e. have structures to enable it to detect the areas which are in use depending upon writing instructions received by the device. This has the advantage that whether areas are in use, can be determined without using storage means.
A further embodiment of the device according to the invention is characterized in that the first detection means are adapted to detect the areas which are in use depending upon use information on the record carrier. This has the advantage that whether areas are in use, can be directly determined from the use information without having to read the relevant areas themselves for this purpose.
A further embodiment of the device according to the invention is characterized in that the initialization apparatus are adapted to write a band-shaped area having a predetermined width. In this case, the non-written boundary areas are at least sufficient through a minimal width for forming a landing area for landing a reading unit of a reading device after a jump has been made. The width is chosen to be such that, in a majority of the standard reading devices, the reading unit will land within this width in the case of a jump. This has the advantage that the partly written record carrier can be read reliably by means of standard reading devices.
A further embodiment of the device according to the invention is characterized in that the initialization apparatus are adapted to write at an instant subsequent to performing a writing instruction, the instant being determined in dependence upon operational circumstances. This has the advantage that a user is hindered as little as possible by the initialization performance.
A further embodiment of the device according to the invention is characterized in that the dummy information is organized as N dummy information blocks, in which N is at least one and the information blocks are provided with position information. In these adjoining areas, the initialization apparatus write dummy information blocks which includes position information in the conventional manner, such as, for example addresses. This has the advantage that the reading unit can determine the position of the reading unit in the conventional manner based on the position information. At a small value of N, the written boundary area may be too small to land the reading unit, but a run-in area will have been formed for locking in reading apparatus prior to reading an information block in the relevant area which is in use. This is an advantage in a reading device according to the invention, which reading device can search the written area because the reading unit approaches the information block via the run-in area and the tracking means and read signal decoding means can lock in.
In accordance with a second aspect of the invention, a record carrier for use in the writing device is characterized in that the record carrier is provided with status information about the non-written or written state of areas on the record carrier, which status information can be reproduced in a predetermined manner. This has the advantage that, after reproducing the status information via the detection apparatus for detecting the written areas, the writing device knows the status of an area which is either written or not written and can therefore quickly decide whether initialization is necessary, because the area does not need to be read first. This requires a shorter time for performing a writing instruction and for initializing, if necessary, adjoining areas.
In accordance with a third aspect of the invention, a reading device is characterized in that the reading device is provided with search apparatus for searching an area written with marks. The reading device can follow the track only via marks and generate position information. When areas which are not contiguous and are separated by non-written areas are read, the reading unit will generally land a short distance ahead of the information block to be read, when a jump to such an area is made. The search means now have the advantage that a written area is searched, for example by displacing the reading unit further towards the jump until marks are found. Consequently, the reading device according to the invention can reliably read a partly written record carrier.
Those skilled in the art will understand the invention and additional objects and advantages of the invention by studying the description of preferred embodiments below with reference to the following drawings which illustrate the features of the appended claims: